| 摘要 |
1488773 Propylene oxide preparation BAYER AG and DEUTSCHE GOLDUND SILBERSCHEIDEANSTALT 28 April 1976 [30 April 1975] 17174/76 Heading C2C The invention comprises a process for the continuous preparation of propylene oxide from propylene and aqueous hydrogen peroxide wherein (a) an aqueous solution containing 10 to 40% by weight of a water-soluble acid catalyst and 20 to 30% by weight of hydrogen peroxide is reacted with propionic acid in a molar ratio of hydrogen peroxide : propionic acid of 3À5 to 5 : 1 at temperatures of from 10‹ to 70‹ C., (b) the resulting reaction mixture is extracted with benzene in counter-current, (c) all or part of the aqueous raffinate from the extraction, which contains in the main hydrogen peroxide and acid catalyst, is reconcentrated by removing water by distillation, (d) the reconcentrated raffinate and the part of the raffinate which has optionally not been reconcentrated are recycled into the reaction stage (a), the concentrations of hydrogen peroxide and water-soluble acid catalyst being made up to those required for the reaction with propionic acid by adding the hydrogen peroxide required to restore the hydrogen peroxide concentration to that required for the reaction with propionic acid to the part of the raffinate which is to be reconcentrated, before or after removal of water by distillation according to (c), or to the part of the raffinate which is optionally not reconcentrated, (e) the benzene extract, which contains in the main perpropionic acid and propionic acid, is treated with water or an aqueous solution, (f) the water-containing benzene extract, which is now virtually free from hydrogen peroxide, is subjected to an azeotropic distillation so that the residual water content in the sump of the azeotrope column is less than 0À5% by weight, (g) the solution, containing perpropionic acid and propionic acid, which is now obtained as the sump product from azeotropic distillation, is reacted with excess propylene at temperatures of from 40‹ to 100‹ C. and at a pressure of from 2 to 30 bars, and (h) the reaction mixture, containing propylene oxide, is worked up in a manner which is in itself known, pure propylene oxide being isolated and the excess propylene which may be present, the propionic acid and the benzene being recovered and the whole or part of these recovered products being recycled into the process. |
